The formation of germ cells during embryogenesis is critical for the continuation of all mammalian species, however, relatively little is known about the genetic and molecular regulation of germ line development and how this can contribute to cancer. As part of my postdoctoral training, I identified a crucial role for PRDM14 during primordial germ cell (PGC) establishment, and demonstrated a novel mechanism through which PRDM14 represses differentiation to other cell lineages by recruiting a cofactor MTGR1 to chromatin. PRDM-containing proteins belong to a structurally conserved SET domain family of histone lysine methyltransferases, but a direct enzymatic activity has only been detected in a small subset of the PRDMs, and my preliminary work provides a first proof-of-principle study that they may instead exert their function by recruiting other protein partners. Therefore, I hypothesize that detailed mapping of PRDM protein-protein interactions will provide us with an understanding of their biological activity. The proposed Aim1 will offer novel mechanistic insights into PRDM14 molecular function and provide a wealth of candidate regulators of germ line development by defining the protein interactome. In the independent portion of the award, I will characterize biochemically and functionally novel PRDM14 interaction as well as provide mechanistic understanding of how this novel partner contributes to germ cell formation and pluripotency. In addition to understanding the molecular pathways governing the normal development of PGCs, it is pivotal to know what goes awry in the disease setting. Remarkably, PRDM14 is repressed in normal adult somatic tissues and its aberrant overexpression is associated with tumor initiation in a wide variety of cancers, with the highest levels observed in testicular germ cell tumors. Germ cell tumors are formed from the misguidance and/or overproliferation of PGCs during early development. In Aim2 of this proposal I will test the contribution of PRDM14 to the disease pathogenesis and identify whether downregulation of PRDM14 decreases the proliferation rates of the cancerous cell lines and sensitizes them to apoptosis and chemotherapy. In the independent phase of this award I will interrogate the molecular factors driving germ cell malignancy and will investigate changes in chromatin landscape and gene expression. Overall, the experiments here will assess the effects of PRDM14 downregulation in cancerous germ cells and contribution of chromatin landscape to gene deregulation in these cancerous cells providing foundation to the development of new PRDM14 therapeutics. Training during the mentored portion of this grant will focus on strengthening my oncology expertise. These skills will complement my undergraduate and graduate training in chromatin biology with the focus on biochemistry and biophysics. Discovering the multifaceted PRDM14 interactions and their involvement in cancers equips me with a unique direction for my independent research. The training provided by this award will be instrumental in achieving my long-term goal of establishing a research program that investigates epigenetic mechanisms of gene regulation, and how their dysregulation leads to disease.